Someone has used my credit how do I fix this?!

About a year ago I tried signing up for a pre paid card they needed my social, for them to know it was really me they asked me odd questions like "What was your first car"

& Which of these family members do you know " …, …, …, …" They were all family members on my dads side who I ve NEVER met in my life.

I recently this year tried signing up for an Amazon credit card since I should have 0 credit I thought I d build, I was denied

Just now I went to a free check your credit service and they say I took out a mortgage in 2011! And have used my credit to buy a car, and got a credit card at a retail store!

I KNOW this wasn t me I wasn t even 18 in 2011 I m going to be 20 THIS YEAR!

Please tell me how I can fix this!

Read more: Someone has used my credit how do I fix this?!